This evolution consists, first in the elaboration of the
underground net systems, then in a long polyphased process
of filling – emptying the karstic voids, according to
the up and down base level changes that occurred almost
continuously during the first half of the Tertiary era. The
filling sediments are mostly vadose clay deposits, the
various ages of which being established from the study
of their fossil vertebrate contents (for latest accounts
see Pélissié & Sigé 2006). Then, since latest Oligocene
times, the Quercy platform was covered with prograding
lacustrine sediments of the Aquitaine Basin. Finally,
the whole structure was strongly worn down by the so-
called Plio-Pleistocene erosional phase: the previously
deep underground system became closer to the surface,
and was exposed both to erosion and widening, but also
Plio-Pleistocene fillings occurred as shown by the fossils
they include (Crochet et al. 2006). Among the latter are
rare Late Pliocene and Plio-Pleistocene tooth specimens.